If until then, the surface of the Antarctic sea ice remained relatively impervious to the effects of global warming, the latest readings show a sharp drop during the month of November. The record for the smallest ice extent was probably also broken last February, in the heart of the austral summer.
Sometimes stable, sometimes even slightly increasing, the surface of the Antarctic sea ice remained until then relatively spared from the effects of global warming, which was not the case at the North Pole for example, the situation now seems to have improved. rapidly degrade there. In fact, last November, the beginning of spring in Antarctica, the extent of the ice dropped sharply, dropping from 16 to 14 million km².
» This is a phenomenon of unprecedented magnitude caused in part by temperatures 2 to 4°C higher than normal for the season. But the precise origin of these high temperatures is still unknown. “, commented David Salas y Mélia, climatologist at the National Center for Meteorological Research of Météo-France during a press conference on Friday March 24, 2017. “ We are now curious to see how the pack ice will settle again next year after this extraordinary rupture. “, he adds. This pack ice is now more than 2 million square kilometers behind the 1981-2010 average, as shown in the graph below.
Since at least the 1970s, the trend of sea ice cover at the South Pole has been stable or even increasing, despite a few episodes of losses that were not nearly as brutal. In view of this notable stall, it seems that the trend is changing. At the North Pole, the sea ice is melting from year to year, but in the south, we did not observe the same phenomenon. Anyway until then.
» This slight extension of the ice surface observed at the South Pole was undoubtedly attributable to three factors “, explains David Salas y Mélia, relayed by S & A. First, a relatively weak mixing between the surface waters and those in depth, whose temperature is a little higher. Second, the strong winds that regularly push the pack ice out to sea, causing an extension effect on the ocean. Finally, the cold waters of the South Pacific usually dig a low pressure system in the Amundsen Sea, giving rise, there too, to winds which contribute to the extension of the ice cover. But then why is Antarctica now suffering the same scourge as the Arctic? For the moment, the data are insufficient to give an answer.
Some signs, however, give some answers, such as this huge crack that appeared west of Antarctica and which is spreading at high speed. It progresses at the speed of 5 football pitches a day and a gigantic piece threatens to come off in the coming months. “, notes the climatologist. » This area, which is the marine extension of the continental ice cap, constitutes a kind of ice plug. If it were to give way, part of what is upstream could also slip in the water. “, he adds.